Underground pipelines of a city are an important component of fundamental facilities of the city, and are compared to “blood vessels” of the city. They cross each other and are distributed in the whole city to construct a dense underground pipeline network of the city. The underground pipelines of the city provide energy sources, information and water for the city all the time, and provide a basis and guarantee for economic development and life of citizens. The number of the underground pipelines is large and data thereof is incomplete, great difficulties are caused in urban planning, development and establishment, scientific management, and correct decision. Accidents such as explosion of gas pipelines and disconnection of communication cables due to blind digging during construction occur frequently, causing great loss for the nation and people. Underground pipeline detection is also very important in terms of archaeology, petroleum, gas and mineral transportation. Therefore, it is necessary to carry out a research on detection and identification of a tubular underground facility.
Definitely, the most common and direct method for detecting failure of a heat-supplying underground tubular facility is manual interpretation; however, this method is very time consuming and the detection is inaccurate, and there is no report on failure-free positioning. The infrared imaging is proposed as a new technology of detecting an underground tubular facility; however, the technology of detecting an underground tubular facility using the infrared imaging around the world all directly use an infrared imaging sensor to perform imaging observation and manual interpretation.
The physical basis of the infrared remote sensing imaging is that a large amount of solar energy irradiated to the soil is absorbed to generate heat, and infrared radiation generated by the heated soil is detected by a thermal infrared sensor. Natural solar energy, after daily circulated heating and cooling, has different effects on a buried object and the land surrounding the object, thereby causing a detectable temperature difference. The existence of the underground tubular facility may cause a planar land surface thermal distribution abnormity, which can be used for detecting and positioning an underground target.
However, the limitations of the above method lie in that: 1. The thermal abnormity of the underground pipeline is conducted and modulated by the stratum in which it is buried, the thermal distribution reaching the land surface changes, which causes a large difference with the underground pipeline form, and is embodied as a greatly reduced thermal diffusion temperature difference and a weak thermal signal, resulting in that not only the position is changed, but also the underground pipeline is hard to be found and positioned; 2. It is difficult to directly use the infrared imaging sensing for performing manual interpretation, and the underground tubular facility cannot be found correctly and intuitively.